/**
 * UGENE - Integrated Bioinformatics Tools.
 * Copyright (C) 2008-2020 UniPro <ugene@unipro.ru>
 * http://ugene.net
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 */

#ifndef _U2_RING_BUF_H_
#define _U2_RING_BUF_H_

namespace U2 {

class RingBuffer {
public:
    RingBuffer(char *buf, int size)
        : data(buf), size(size), len(0), start(0) {
    }
    inline int read(char *dest, int n, int index = 0) const;
    inline void append(const char *src, int n);
    int length() const {
        return len;
    }
    char *rawData() const {
        return data;
    }

private:
    char *data;    // buffer area
    int size;    // buffer size
    int len;    // length of buffered data
    int start;    // start offset
};

int RingBuffer::read(char *dest, int n, int index) const {
    assert(index < len);
    if (n > len - index) {
        n = len - index;
    }
    int begin = (start + index) % size;
    int end = (start + index + n) % size;
    if (begin < end) {
        memcpy(dest, data + begin, n);
    } else {
        assert(end + size - begin >= n);
        int l1 = qMin(n, size - begin);
        memcpy(dest, data + begin, l1);
        if (l1 < n) {
            memcpy(dest + l1, data, n - l1);
        }
    }
    return n;
}

void RingBuffer::append(const char *src, int n) {
    if (n >= size) {
        start = 0;
        len = size;
        memcpy(data, src + n - size, size);
    } else {
        int trail_len = qMin(len, size - n);
        int trail_start = (start + len - trail_len) % size;
        int trail_end = (start + len) % size;
        if (trail_start > trail_end) {
            assert(trail_start - trail_end >= n);
            memcpy(data + trail_end, src, n);
        } else {
            assert(trail_start + size - trail_end >= n);
            int l1 = qMin(size - trail_end, n);
            memcpy(data + trail_end, src, l1);
            if (l1 < n) {
                memcpy(data, src + l1, n - l1);
            }
        }
        start = trail_start;
        len += n;
        if (len > size)
            len = size;
    }
}

}    // namespace U2

#endif
